In order to stabilize a convey-crane with only cart position measurement, this paper designs an additional dynamics with which the parallel-connected system is feedback passive. Since the crane system can be stabilized with a proportional-derivative (PD) law, the additional system is constructed by using the PD gains, and the closed-loop system exhibits almost same performances with the PD law. With the proposed control law, the transfer function of the additional system has the form of sH(s) with a strictly positive real (SPR) H(s).